The ability of the analog measurement systems to produce a signal that accurately represents a physical parameter is directly related to the accuracy and stability of the system components. Typically, the parameters which describe the operation of a system component vary according to certain environmental factors such as time and temperature. As a consequence of this variation the accuracy of a system component can be reduced thereby reducing the accuracy of the entire system. Since a typical analog measurement system includes several system components there can be an accumulation of errors that seriously compromises the accuracy of the system.
The prior art sought to deal with this problem by specifying component tolerances and environmental dependency coefficients that reduced system variation to an acceptable limit. For example, a parameter associated with the operation of a system component could be maintained within a tolerance of a specified value over a specified temperature range by a feedback circuit. However, analog systems which utilize such techniques are extremely complex and costly. Consequently, among the objectives of the present invention are the reduction of complex and costly circuitry to maintain the stability and accuracy of system components while at the same time producing an accurate analog measurement signal.